Preface
At length I pass to the remaining portion of my Ethics，which is concerned with the way leading to freedom。I shall therefore treat therein of the power of the reason，show-ing how far the reason can control the emotions，and what is the nature of Mental Free-dom or Blessedness；we shall then be able to see，how much more powerful the wise man is than the ignorant。It is no part of my design to point out the method and means whereby the understanding may be perfected，nor to show the skill whereby the body may be so tended，as to be capable of the due performance of its functions。The latter question lies in the province of Medicine，the former in the province of Logic。Here，therefore，I repeat，I shall treat only of the power of the mind，or of reason；and I shall mainly show the extent and nature of its dominion over the emotions，for their control and moderation。That we do not possess absolute dominion over them，I have already shown。Yet the Stoics have thought，that the emotions depended absolutely on our will，and that we could absolutely govern them。But these philosophers were compelled，by the protest of experience，not from their own principles，to confess，that no slight prac-tice and zeal is needed to control and moderate them；and this someone endeavoured to illustrate by the example（if I remember rightly）of two dogs，the one a house-dog and the other a hunting-dog。For by long training it could be brought about，that the house-dog should become accustomed to hunt，and the hunting-dog to cease from running after hares。To this opinion Descartes not a little inclines。For he maintained，that the soul or mind is specially united to a particular part of the brain，namely，to that part called the pineal gland，by the aid of which the mind is enabled to feel all the movements which are set going in the body，and also external objects，and which the mind by a simple act of volition can put in motion in various ways。He asserted，that this gland is so suspen-ded in the midst of the brain，that it could be moved by the slightest motion of the animal spirits；further，that this gland is suspended in the midst of the brain in as many different manners，as the animal spirits can impinge thereon；and，again，that as many different marks are impressed on the said gland，as there are different external objects which impel the animal spirits towards it；whence it follows，that if the will of the soul suspends the gland in a position，wherein it has already been suspended once before by the animal spirits driven in one way or another，the gland in its turn reacts on the said spirits，driving and determining them to the condition wherein they were，when repulsed before by a similar position of the gland。He further asserted，that every act of mental volition is united in nature to a certain given motion of the gland。For instance，whenev-er anyone desires to look at a remote object，the act of volition causes the pupil of the eye to dilate，whereas，if the person in question had only thought of the dilatation of the pupil，the mere wish to dilate it would not have brought about the result，inasmuch as the motion of the gland，which serves to impel the animal spirits towards the optic nerve in a way which would dilate or contract the pupil，is not associated in nature with the wish to dilate or contract the pupil，but with the wish to look at remote or very near ob-jects。Lastly，he maintained that，although every motion of the aforesaid gland seems to have been united by nature to one particular thought out of the whole number of our thoughts from the very beginning of our life，yet it can nevertheless become through ha-bituation associated with other thoughts。
He thence concludes，that there is no soul so weak，that it cannot，under proper direction，acquire absolute power over its passions。For passions as defined by him are“perceptions，or feelings，or emotions of the soul，which are particularly related to the soul，and which are produced，preserved，and strengthened by some motion of the spir-its”（see The Passions of the Soul 1，27）。But，seeing that we can join any motion of the gland，or consequently of the spirits，to any volition，the determination of the will depends entirely on our own powers；if，therefore，we determine our will with sure and firm decisions in the direction to which we wish our actions to tend，and associate the motions of the passions which we wish to acquire with the said decisions，we shall ac-quire an absolute dominion over our passions。
Such is the doctrine of this illustrious philosopher（in so far as I gather it from his own words）；it is one which，had it been less ingenious，I could hardly believe to have proceeded from so great a man。Indeed，I am lost in wonder，that a philosopher，who had stoutly asserted，that he would draw no conclusions which do not follow from self-evident premisses，and would affirm nothing which he did not clearly and distinctly per-ceive，and who had so often taken to task the scholastics for wishing to explain obscuri-ties through occult qualities，could maintain a hypothesis，beside which occult qualities are commonplace。What does he understand，I ask，by the union of the mind and the body？What clear and distinct conception has he got of thought in most intimate union with a certain particle of extended matter？Truly I should like him to explain this union through its proximate cause。But he had so distinct a conception of mind being distinct from body，that he could not assign any particular cause of the union between the two，or of the mind itself，but was obliged to have recourse to the cause of the whole uni-verse，that is to God。Further，I should much like to know，what degree of motion the mind can impart to this pineal gland，and with what force can it hold it suspended？For I am in ignorance，whether this gland can be agitated more slowly or more quickly by the mind than by the animal spirits，and whether the motions of the passions，which we have closely united with firm decisions，cannot be again disjoined therefrom by physical causes；in which case it would follow that，although the mind firmly intended to face a given danger，and had united to this decision the motions of boldness，yet at the sight of the danger the gland might become suspended in a way，which would preclude the mind thinking of anything except running away。In truth，as there is no common standard of volition and motion，so is there no comparison possible between the powers of the mind and the power or strength of the body；consequently the strength of one cannot in any wise be determined by the strength of the other。We may also add，that there is no gland discoverable in the midst of the brain，so placed that it can thus easily be set in motion in so many ways，and also that all the nerves are not prolonged so far as the cavities of the brain。Lastly，I omit all the assertions which he makes concerning the will and its freedom，inasmuch as I have abundantly proved that his premisses are false。Therefore，since the power of the mind，as I have shown above，is defined by the understanding only，we shall determine solely by the knowledge of the mind the remedies against the e-motions，which I believe all have had experience of，but do not accurately observe or distinctly see，and from the same basis we shall deduce all those conclusions，which have regard to the mind s blessedness。
Axioms
1.If two contrary actions be started in the same subject，a change must necessarily take place，either in both，or in one of the two，and continue until they cease to be con-trary。
2.The power of an effect is defined by the power of its cause，in so far as its es-sence is explained or defined by the essence of its cause。
Propositions
PROP。1.Even as thoughts and the ideas of things are arranged and associated in the mind，so are the modifications of body or the images of things precisely in the same way arranged and associated in the body。
Proof。-The order and connection of ideas is the same as the order and connection of things，and vice versa the order and connection of things is the same as the order and connection of ideas。Wherefore，even as the order and connection of ideas in the mind takes place according to the order and association of modifications of the body，so vice versa the order and connection of modifications of the body takes place in accordance with the manner，in which thoughts and the ideas of things are arranged and associated in the mind。
PROP。2.If we remove a disturbance of the spirit，or emotion，from the thought of an external cause，and unite it to other thoughts then will the love or hatred towards that external cause，and also the vacillations of spirit which arise from these emotions，be destroyed。
Proof。-That，which constitutes the reality of love or hatred，is pleasure or pain，accompanied by the idea of an external cause；wherefore，when this cause is removed，the reality of love or hatred is removed with it；therefore these emotions and those which arise therefrom are destroyed。
PROP。3.An emotion，which is a passion，ceases to be a passion，as soon as we form a clear and distinct idea thereof。
Proof。-An emotion，which is a passion，is a confused idea。If，therefore，we form a clear and distinct idea of a given emotion，that idea will only be distinguished from the emotion，in so far as it is referred to the mind only，by reason；therefore，the emotion will cease to be a passion。
Corollary。-An emotion therefore becomes more under our control，and the mind is less passive in respect to it，in Proportion as it is more known to us。
PROP。4.There is no modification of the body，whereof we cannot form some clear and distinct conception。
Proof。-Properties which are common to all things can only be conceived adequate-ly；therefore there is no modification of the body，whereof we cannot form some clear and distinct conception。
Corollary。-Hence it follows that there is no emotion，whereof we cannot form some clear and distinct conception。For an emotion is the idea of a modification of the body，and must therefore involve some clear and distinct conception。
PROP。5.An emotion towards a thing，which we conceive simply，and not as nec-essary，or as contingent，or as possible，is，other conditions being equal，greater than any other emotion。
Proof。-An emotion towards a thing，which we conceive to be free，is greater than one towards what we conceive to be necessary，and，consequently，still greater than one towards what we conceive as possible，or contingent。But to conceive a thing as free can be nothing else than to conceive it simply，while we are in ignorance of the causes whereby it has been determined to action；therefore，an emotion towards a thing which we conceive simply is，other conditions being equal，greater than one，which we feel to-wards what is necessary，possible，or contingent，and，consequently，it is the greatest of all。
PROP。6.The mind has greater power over the emotions and is less subject there-to，in so far as it understands all things as necessary。
Proof。The mind understands all things to be necessary and to be determined to existence and operation by an infinite chain of causes；therefore，it thus far brings it a-bout，that it is less subject to the emotions arising therefrom，and feels less emotion to-wards the things themselves。
PROP。7.Emotions which are aroused or spring from reason，if we take account of time，are stronger than those，which are attributable to particular objects that we regard as absent。
Proof。-We do not regard a thing as absent，by reason of the emotion wherewith we conceive it，but by reason of the body，being affected by another emotion excluding the existence of the said thing。Wherefore，the emotion，which is referred to the thing which we regard as absent，is not of a nature to overcome the rest of a man s activities and power，but is，on the contrary，of a nature to be in some sort controlled by the emo-tions，which exclude the existence of its external cause。But an emotion which springs from reason is necessarily referred to the common Properties of things，which we always regard as present（for there can be nothing to exclude their present existence），and which we always conceive in the same manner。Wherefore an emotion of this kind al-ways remains the same；and consequently emotions，which are contrary thereto and are not kept going by their external causes，will be obliged to adapt themselves to it more and more，until they are no longer contrary to it；to this extent the emotion which springs from reason is more powerful。
PROP。8.An emotion is stronger in Proportion to the number of simultaneous con-current causes whereby it is aroused。
Proof。-Many simultaneous causes are more powerful than a few；therefore，in Proportion to the increased number of simultaneous causes whereby it is aroused，an e-motion becomes stronger。
PROP。9.An emotion，which is attributable to many and diverse causes which the mind regards as simultaneous with the emotion itself，is less hurtful，and we are less subject thereto and less affected towards each of its causes，than if it were a different and equally powerful emotion attributable to fewer causes or to a single cause。
Proof。-An emotion is only bad or hurtful，in so far as it hinders the mind from be-ing able to think；therefore，an emotion，whereby the mind is determined to the contem-plation of several things at once，is less hurtful than another equally powerful emotion，which so engrosses the mind in the single contemplation of a few objects or of one，that it is unable to think of anything else；this was our first point。Again，as the mind s es-sence，in other words，its power，consists solely in thought，the mind is less passive in respect to an emotion，which causes it to think of several things at once，than in regard to an equally strong emotion，which keeps it engrossed in the contemplation of a few or of a single object；this was our second point。Lastly，this emotion，in so far as it is at-tributable to several causes，is less powerful in regard to each of them。